In recent years, various electric devices have been mounted on vehicles. For example, in electric vehicles, a power converter that converts electric power output from a DC power source into electric power for driving a motor is mounted. In an electric vehicle described in Japanese Patent Application Publication No. 2018-24330 (Patent Document 1), an electric power control unit that controls electric power for driving a traction motor is fixed onto a motor casing. If the casing of the electric device to which a high voltage is applied is damaged by a collision impact, a high-voltage-applied component of the electric device may be exposed from the casing. In the electric vehicle described in Patent Document 1, the electric power control unit is supported on the motor casing by a front bracket and a rear bracket. When such an electric vehicle collides at its front with an obstacle, the bracket is deformed to displace the electric power control unit, thereby reducing a collision impact applied onto the electric power control unit.
Patent Document 1 describes a technique for preventing the motor casing from being damaged due to an impact applied to the motor casing through the rear bracket. The rear bracket is attached to the motor casing by a first bolt disposed at a front side and a second bolt disposed at a rear side. The rear bracket is provided with a first insertion hole into which the first bolt is inserted and a second insertion hole into which the second bolt is inserted. A gap (clearance) between the second bolt and the second insertion hole is larger than a gap between the first bolt and the first insertion hole. In addition, a portion of the motor casing with the first bolt attached thereto has a higher strength than a portion of the motor casing with the second bolt attached thereto. In the structure described in Patent Document 1, the gap between the second bolt and the second insertion hole is larger than the gap between the first bolt and the first insertion hole. Due to this, if a collision impact is applied from the front side of the vehicle to the rear bracket, a larger load is applied onto the first insertion hole having the small gap than the second insertion hole having the large gap. In short, a larger load is applied onto a high-strength area around the first insertion hole, whereas a relatively small load is applied onto a low-strength area around the second insertion hole. Consequently, the collision impact is dispersed depending on the strength of the portion of the motor casing, so that the motor casing is less likely to be damaged.